The invention relates to a domestic appliance comprising a power supply connection, a generator tube for generating electromagnetic radiation, first switching means connected in series with the generator tube, and a programming device which comprises an input for receiving on-time information and a subsequent start signal, an output for supplying an activation signal for the first switching means, updating means for updating the on-time yet to be completed, and first detection means for detecting said updating and for generating, in the case of a failure therein, an error signal in order to deactivate said activation signal. A device of this kind is known from U.S. Pat. No. 4,189,665, issued Feb. 19, 1980. This appliance is an irradiation device with a discharge tube for supplying ultraviolet radiation. The discharge tube is filled with a gas or vapour and the radiation generated is used for therapeutic, prophylactic or cosmetic purposes. A plurality of discharge tubes may be present. An excessive does of ultraviolet radiation is particularly undesirable, notably if it is produced because the apparatus is not switched off. In the known device the irradiation time is determined by the discharging of a capacitor via a variable resistor. If the discharge current drops below a given value, the irradiation is terminated. Thus, a single level of protection is provided which becomes ineffective if the switch continuously remains in the closed condition due to a fault. In that case the known device may still be used by providing , for example, an additional external switch in series for example, externally. This pseudo-repair can be performed by the user and results in unprotected operation. Furthermore, the transistor which serves to activate the termination of the radiation could become defective. In that case, operation can be continued with an apparatus which is no longer protected. However, it can still produce correct irradiation times as long as no further fault occurs.
Problems of this kind also occur in, for example, domestic ovens utilizing electromagnetic radiation. The generator is then, for example, a magnetron tube and the wavelength of the radiation used is in the centimeter and decimeter range.